How do I tell what gear ratio I have in my Chevy truck?

The gear ratio in your Chevy truck is an important piece of information that can help you understand your vehicle's performance and capabilities. Knowing your gear ratio can assist with tasks like towing, off-road driving, and fuel efficiency. In this article, we'll provide a step-by-step guide on how to determine the gear ratio in your Chevy truck.

What is a Gear Ratio?

The gear ratio is a measure of the relationship between the number of rotations of the input shaft (the driveshaft) and the number of rotations of the output shaft (the rear axle). It determines how much torque is transferred from the engine to the wheels. A higher gear ratio means the wheels will turn fewer times for each rotation of the driveshaft, resulting in more torque but lower top speed. A lower gear ratio means the wheels will turn more times for each rotation of the driveshaft, resulting in less torque but higher top speed.

How to Find the Gear Ratio in Your Chevy Truck

To determine the gear ratio in your Chevy truck, you'll need to follow these steps:

• Locate the rear axle tag or sticker on your truck. This is usually found on the rear differential housing or the frame near the rear axle.


• The rear axle tag will list the gear ratio, which will be expressed as a ratio, such as 3.73:1 or 4.10:1.


• The first number in the ratio represents the number of times the driveshaft rotates for each rotation of the rear wheels. The second number represents the number of times the rear wheels rotate.


• For example, a gear ratio of 3.73:1 means the driveshaft rotates 3.73 times for every one rotation of the rear wheels.

If you can't find the rear axle tag or sticker, you can also determine the gear ratio by consulting your owner's manual or contacting your local Chevy dealer.

Why Knowing Your Gear Ratio is Important

Knowing the gear ratio in your Chevy truck is important for several reasons:

• Towing Capacity: The gear ratio affects your truck's towing capacity. A higher gear ratio (e.g., 4.10:1) will provide more torque for towing heavy loads, while a lower gear ratio (e.g., 3.73:1) may be better for fuel efficiency and highway driving.


• Off-Road Performance: If you plan to use your Chevy truck for off-road adventures, a higher gear ratio can provide more low-end torque for climbing hills and navigating rough terrain.


• Fuel Efficiency: The gear ratio can also impact your truck's fuel efficiency. A lower gear ratio may result in better fuel economy on the highway, while a higher gear ratio may be more efficient for towing or off-road use.

Knowing your Chevy truck's gear ratio can help you make informed decisions about modifications, accessories, and driving conditions to optimize its performance and efficiency.

Does the VIN number tell you the gear ratio?

You can find a vehicle's gear ratio by using its VIN with a VIN decoder, but the gear ratio isn't always directly encoded in the VIN and may be represented by an axle code. It is best to use an online VIN decoder to check for this information, or to look for a specific axle code on a sticker in the driver's side doorjamb or on the vehicle's build sheet. If a VIN decoder doesn't provide the gear ratio, you can check the vehicle's documentation, the manufacturer's website, or look for a tag on the rear differential itself. 
This video explains how to find the gear ratio using the VIN: 1mVehicle FreakYouTube · Oct 23, 2023
Method 1: Use a VIN decoder 

1. Locate the VIN: Find the 17-digit VIN on your vehicle's dashboard, driver's side doorjamb, or registration. 
2. Enter the VIN: Go to an online VIN decoder, such as the one on the National Highway Traffic Safety Administration (NHTSA) website, or the Mopar VIN decoder. 
3. Check for gear ratio information: The decoder should show the vehicle's specifications. If the gear ratio is available through the VIN, it will be listed here. Some decoders may show an axle code that you can use to find the specific ratio. 

Method 2: Check for axle codes

• Look for a sticker on the inside of the driver's side doorjamb. This sticker often contains an axle code that corresponds to a specific gear ratio. 
• Check your vehicle's original window sticker or build sheet for an axle ratio listed. 
• Look for a tag or stamp on the rear differential cover itself, as this will often have a ratio stamped on it. 

This video shows how to find the axle ratio code on the door jamb sticker: 1mTech28YouTube · Sep 30, 2023
Method 3: Contact the manufacturer

• If other methods don't provide the answer, call the vehicle manufacturer or a dealership with your VIN. They can look up your specific vehicle's original specifications, including the gear ratio. 

You can also watch this video to learn how to get gear ratio information from the manufacturer: 1mChris DukeYouTube · Nov 22, 2016

How to find gear ratio on a Chevy truck?

Identify your GMC or Chevrolet rear end gear ratio by the RPO Codes, usually located on the placard labeled “Service Parts Identification” inside the drivers door panel or glove box.

How do you tell if you have 3.73 or 4.10 gears?

You can tell if you have 373 or 410 gears by checking the differential cover's metal tag for a stamped ratio, counting the teeth on the ring and pinion gears, or rotating the wheel and counting the driveshaft revolutions. The tag is the easiest method, but counting teeth is more precise if the tag is missing. The wheel-spinning method works with the vehicle jacked up but requires careful counting.
 
Method 1: Check the differential tag 
This video shows how to find the gear ratio from a tag on the differential cover: 59sWebWheelerYouTube · Apr 10, 2018

1. Locate the differential cover on the rear axle.
2. Look for a small metal tag bolted to the differential cover, often held by one of the bolts.
3. Clean the tag if necessary and look for a three-digit number like "3.73" or "4.10". 

Method 2: Count the teeth on the gears 
You can watch this video to learn how to count the teeth on the ring and pinion gears: 59sBleepinJeepYouTube · Dec 26, 2015

1. Drain the differential fluid and remove the differential cover bolts to access the gears. 
2. Count the teeth on the large ring gear and the small pinion gear. The number of ring gear teeth is usually a larger number (e.g., 41) and the pinion gear teeth is a smaller number (e.g., 10). 
3. Divide the number of ring gear teeth by the number of pinion gear teeth to get the ratio. 
   • A 373 ratio will result from a division where the result is approximately 3.733.733.73 (e.g., 41 ring teeth / 11 pinion teeth ≈3.727is approximately equal to 3.727≈3.727). 
   • A 410 ratio will result from a division where the result is approximately 4.104.104.10 (e.g., 41 ring teeth / 10 pinion teeth =4.1equals 4.1=4.1). 

Method 3: Rotate the wheel and count driveshaft turns 
This video demonstrates how to count the driveshaft rotations to find the gear ratio: 48sBent Motorsports OffroadYouTube · Sep 22, 2023

1. Jack up the rear of the vehicle and secure it on jack stands. 
2. Mark one of the rear wheels and the driveshaft with a piece of tape or a marker. 
3. For an open differential, have an assistant hold the other rear wheel still, or use a different method to ensure only one wheel can spin freely. 
4. For an open differential, rotate the marked wheel one full revolution and count how many times the driveshaft rotates. You will need to multiply this number by two. 
5. For an open differential, rotate the marked wheel two full revolutions and count the number of times the driveshaft rotates. 
6. For a locked differential, lift both rear wheels and rotate one of them one full revolution, counting the driveshaft turns. 
7. Compare the number of driveshaft turns to the expected ratios: 
   • 3.73 ratio: The driveshaft will turn approximately 3.733.733.73 times for every single revolution of the tire. 
   • 4.10 ratio: The driveshaft will turn approximately 4.104.104.10 times for every single revolution of the tire. 

Where is the gear ratio stamped?

The gear ratio is most often stamped on a metal tag on the differential cover, or directly on the ring gear itself inside the differential housing. It may also be found on the vehicle's original window sticker (Monroney) or a build sheet, and sometimes on a data tag on the axle itself.
 
Common locations to find the gear ratio

• Differential cover tag: Look for a small metal tag attached to one of the differential cover bolts. The ratio will be stamped or printed on it, notes this YouTube video. 
• Ring gear: If the tag is missing or unreadable, you may be able to see the ratio stamped directly on the edge of the ring gear after removing the differential cover. 
• Axle or transfer case tag: Some axles or transfer cases have a separate data tag that contains the gear ratio. 
• Window sticker or build sheet: The original window sticker (Monroney) or a build sheet will list the factory-installed gear ratio. 
• VIN decoder: You can sometimes find the gear ratio by using the VIN on an online decoder or by checking the vehicle's digital glove box information. 
• Bill of Materials (BOM): For Dana differentials, you can use the BOM number found on the tag to look up the original specs online, which includes the gear ratio and other components. 

Alternative method (if you can't find a stamp)
If the gear ratio is not stamped anywhere visible, you can determine it yourself by rotating the wheel and driveshaft. 

• Safely lift and support the rear axle so that the rear wheels are off the ground.
• Place the transmission in neutral.
• Mark the driveshaft and one of the rear tires with chalk or tape.
• Spin the marked tire exactly one full revolution.
• Count how many times the driveshaft has rotated.
• The number of driveshaft rotations is approximately your gear ratio. For example, if the driveshaft turns 3.55 times for one tire rotation, your ratio is about 3.55.